NoQ, doable but pollutes file system, wasting at least 50 MB which is sometimes quite precious (yeah, I own 500 GB HDD for few months only, so I know what I'm talking about, but don't want to discuss it further ) so I would suggest installing it to some directory in ~/ and then delete build directory (preferably 2.3.9 version should land in local directory since it won't receive any official updates).

Nadszedł już czas, najwyższy czas, nienawiść zniszczyć w sobie.
The time has come, the high time, to destroy hatred in oneself.

[dark]_Continue, start with 3.1 (since it works better than 2.3.9 for campaign), in worst case you will need to stick with specific version with which you will start, however risk of breaking compatibility due to bugfixes should low.

Nadszedł już czas, najwyższy czas, nienawiść zniszczyć w sobie.
The time has come, the high time, to destroy hatred in oneself.

Good morning team, first want to congratulate you all for your commitment and quality of the game, and I really enjoyed playing it more.
I played version 2.9 and worked perfectly, even destroy all the structures of Nexus, and pick up the artifacts chassis revenge, arcangel missiles, cannon Gaus (Gama in the campaign), but the game has not finalized the chapter, did not perform the boot "mission completed, "so I could not finish this exciting game.
I decided to install version 3.1, I really liked the changes, but often occur, two errors, Windows says that the the game stopped working and will close the program, and the game is crashed (I have some files from the crash), this way, I can not keep playing the latest version.
I really need help, I really want to finish the campaign in this great game.
Thank you for your attention!

Campos Zidov wrote:Good morning team, first want to congratulate you all for your commitment and quality of the game, and I really enjoyed playing it more.
I played version 2.9 and worked perfectly, even destroy all the structures of Nexus, and pick up the artifacts chassis revenge, arcangel missiles, cannon Gaus (Gama in the campaign), but the game has not finalized the chapter, did not perform the boot "mission completed, "so I could not finish this exciting game.
I decided to install version 3.1, I really liked the changes, but often occur, two errors, Windows says that the the game stopped working and will close the program, and the game is crashed (I have some files from the crash), this way, I can not keep playing the latest version.
I really need help, I really want to finish the campaign in this great game.
Thank you for your attention!